import pygame
from pygame.sprite import Sprite

class Ship(Sprite):
    '''管理飞船的类'''

    def __init__(self,ai_game):
        '''初始化飞船并设置其初始化位置'''
        super().__init__()
        self.screen = ai_game.screen
        '''设置飞船速度'''
        self.settings = ai_game.settings

        self.screen_rect = ai_game.screen.get_rect()

        '''加载飞船图像并获取其外接矩阵'''
        self.image = pygame.image.load('image/ship.bmp')
        self.rect = self.image.get_rect()

        '''对于每艘新飞船，都将其放在屏幕底部的中央'''
        self.rect.midbottom = self.screen_rect.midbottom

        '''在飞船的属性x中存储小数值'''
        self.x = float(self.rect.x)

        '''移动标志'''
        self.moving_right = False
        self.moving_left = False

    def update(self):
        '''根据移动标志调整飞船的位置'''
        '''更新飞船而不是rect对象的值'''
        if self.moving_right and self.rect.right < self.screen_rect.right:
            self.x += self.settings.ship_speed
        if self.moving_left and self.rect.left > 0:
            self.x -= self.settings.ship_speed

        '''根据self.x更新rect对象'''
        self.rect.x = self.x

    def blitme(self):
        '''在指定位置绘制飞船'''
        self.screen.blit(self.image, self.rect)

    def center_ship(self):
        '''让飞船在屏幕底端剧中'''
        self.rect.midbottom = self.screen_rect.midbottom
        self.x = float(self.rect.x)
